Path Of Totality, Umbra And Penumbra

Solar eclipses, due to the conditions they need to bring together, are a rare phenomenon. On August 21, 2017 will be a solar eclipse visible from the United States that the team of Vaonis won’t miss for anything and who will record the event with its smart telescope Stellina. While waiting for the event, we give you some explanations on this singular astronomical phenomenon. After talking about the conditions of observation of an eclipse, here is some information about the different zones from where you can watch an eclipse.

The path of totality

Solar eclipses are observable in the shadow zone created by the Moon’s occultation of the Sun. In the case of a total eclipse and only in this one, the shadow zone where it is possible to observe this phenomenon of total eclipse is called “path of totality“.

Author: Wolfgang Strickling

The shadow of the Moon moves from West to East on Earth. The projection of its shadow on the Earth all along its trajectory is called “shadow band“. The width of the shadow band varies depending on the apparent size of the Moon and can reach up to 250 kilometers if the apparent diameter is important.

View solar eclipses from the path of totality

From the path of totality, it is possible to correctly observe the five phases of a total solar eclipse. At first, we observe the first contact between the Sun and the Moon when the two contours touch for the first time. Then, the Moon will continue its progression until the second contact, when the Sun will have completely disappeared to finally reach the maximum of the eclipse at the level of the perfect alignment of the two bodies. The third contact will then be observable soon after and will be the last moment when the Sun will be completely obscured by the Moon. At the end of the eclipse, we observe the fourth and last contact before it finally ends.

Penumbra

Si le phénomène d’éclipse totale n’est lui visible que depuis la bande de totalité, l’éclipse peut quant à elle être observée depuis une zone plus large. De part et d’autre de la bande de totalité, il est possible de constater un phénomène de pénombre. Pour les personnes ne pouvant pas se rendre au niveau de la bande de totalité, se trouver dans la zone créée par le cône de pénombre peut-être une alternative pour observer non pas une éclipse totale mais une éclipse partielle où seulement une partie du soleil serait cachée par l’un des côtés de la Lune.
If the phenomenon of total solar eclipse is only visible from the path of totality, the eclipse can be observed from a wider area. On both sides of the totality band, it is possible to observe a phenomenon of penumbra. For people who are not able to travel somewhere inside the path of totality, being in the zone created by the penumbra may be an alternative to observe not a total eclipse but a partial eclipse where only a part of the sun would be hidden by one side of the moon.